1. Field of the Invention
The present invention relates to an imaging device which contributes to the reduced thickness of a camera.
2. Background Arts
A digital camera and a video camera, which rapidly become pervasive in recent years, are provided with an imaging device chip such as a CCD image sensor, a CMOS image sensor, and the like. The imaging device chip photoelectrically transfers an image which is optically formed on a light receiving surface into image signals. The outputted image signals are sent to an image signal processing circuit, for example, and the image is displayed on an LCD. To obtain the sharp image over the whole picture frame, it is necessary to install the imaging device chip in such a manner that the light receiving surface is perpendicular to an optical axis. Accordingly, various types of imaging devices are suggested.
Japanese Patent Laid-Open Publication No. 61-138909, for example, discloses a solid-state image sensor unit having an inclination adjustment device. The inclination adjustment device has a fixed base board fixed on a flange of a lens barrel, and a movable base board secured to the fixed base board with screws. The movable base board, secured to the fixed base board with the two screws via coil springs, is always in contact with a shaft member provided at the center of the fixed base board by the bias of the springs. An imaging device chip is fixed on the movable base board, and a substrate is disposed in the rearward of the movable base board. The inclination adjustment device adjusts the inclination of the imaging device chip against an optical axis by means of tightening and loosing the two screws.
In order to prevent dust from adhering to an exposed light receiving surface, it is generally known that an imaging device package, comprising an imaging device chip and a package for tightly containing the imaging device chip, is installed in a digital camera and the like.
Japanese Patent Laid-Open Publication No. 61-245773, for example, discloses a video camera having an imaging device chip which is contained in a ceramic package. The imaging device chip maintains a predetermined physical relation with the ceramic package, and the ceramic package keeps a light receiving surface of the imaging device chip in parallel with the front surface of a fixed base board. The ceramic package, the position of which is fixed by two positioning pins, is secured to a flange of a lens barrel with screws.
In the imaging device package described above, however, it is difficult to miniaturize a camera. Accordingly, Japanese Patent Laid-Open Publication No. 7-202152 discloses a solid-state imaging device in which an airtight sealing section including a transparent member covers an only light receiving surface having micro lenses in order to miniaturize a camera.
Japanese Patent Laid-Open Publication No. 9-18649 discloses a document reader in which a bare imaging device chip is installed. The bare imaging device chip is fixed on a substrate. The substrate forms enclosed space together with an optical lens and a camera body (a lens barrel). Since the bare imaging device chip is disposed inside the enclosed space, dust does not adhere to the light receiving surface.
In any of these cases described above, however, the substrate or the base board for positioning is disposed in the rearward of the imaging device, so that it is impossible to shorten the length of the camera in an optical axis direction. In other words, there is a disadvantage in miniaturizing the camera because the thickness of the camera cannot be slimmed.
It is necessary for preventing reduction in magnifying power and optical performance of a taking lens to maintain a predetermined optical length. To slim the camera with maintaining the optical length, it is effective to reduce a dimension backward of the light receiving surface of the imaging device chip (a direction opposite to the taking lens). Accordingly, it is considerable to fix the imaging device chip on the substrate in such a manner that the light receiving surface is exposed through an opening formed in the substrate. In this case, the thickness of the substrate is included in the optical length, so that it is possible to slim the camera without reducing the magnifying power and optical performance of the taking lens.
Japanese Patent Laid-Open Publication No. 11-191865 discloses a solid-state imaging device including an imaging device unit which comprises an imaging device chip (a CCD chip), a film carrier, a transparent member, and a lens integral with a lens barrel. The imaging device unit is fixed to a substrate in such a manner as to be inserted into an opening formed in the substrate. Sealant composed of epoxy resin is charged between the film carrier and the periphery of the imaging device chip, for the purpose of protecting the imaging device chip from moisture and the like.
According to the imaging device of the Japanese Patent Laid-Open Publication No. 11-191865, complex soldering process is needed, because the inner leads of the imaging device chip are soldered to the film carrier, and the outer leads of the film carrier are soldered to the junction land of the substrate. Charging process of the sealant also has to be carried out after the soldering. Therefore, there is a disadvantage that the imaging device results in increase in cost due to complex manufacturing process for actualizing the complex structure thereof.